A color image is usually obtained from a color light sensitive material in the following manner. The color light sensitive material is applied with a color reproduction carried out in a commonly applicable subtractive color process. After exposing the light sensitive material to light imagewise, the exposed silver halide grains are developed with a color developer. The resulting oxidized products of a color developing agent is reacted with each of yellow, magenta and cyan dye forming couplers. Then, bleach-fixing and washing or stabilizing treatments are carried out.
For the resulting color images, image quality improvements including, particularly, color reproduction and image sharpness improvements, are essential. For improving the color reproducibility of color light sensitive materials, yellow couplers excellent in color reproducibility are disclosed in Japanese Patent Application Open to Public Inspection (hereinafter referred to as JP OPI Publication) Nos. 2-189543/1990 and 3-9349/1991. The light sensitive materials applied with this type of yellow couplers are excellent in color reproducibility, but have a defect that the black backgrounds cannot be solid. Particularly when fine lines such as black letters are tried to be reproduced, the above-mentioned defect is so serious that image sharpness is deteriorated.
As for the techniques for improving the above-mentioned black background solidness, for example, JP OPI Publication Nos. 53-133432/1978 and 55-59462/1980 disclose the techniques in which the black background reproducibility is tried to be improved by making use of a color photographic light sensitive material provided with a black image forming layer. According to the techniques, black background reproducibility can be improved, but it was found that the techniques have the defects such as an image sharpness deterioration and an unsatisfactory black color reproducibility on fine lines such as black letters.
Besides the above, the techniques for improving an image sharpness, a technique has been disclosed in which an anti-irradiation dye is used and another technique in which black colloidal silver is used. However, these techniques have, for example, a problem of a serious sensitivity deterioration induced thereby, and another problem of a stain which remains on the white background after completing the treatment. For preventing the sharpness deterioration of a reflection type support, JP OPI Publication Nos. 54-46035/1979, 2-28640/1990 and 3-89340/1991 and Japanese Patent Examined Publication (hereinafter referred to as JP Examined Publication) Nos. 59-820/1984 and 2-29203/1990 disclose a proposal for increasing the filling ratios of a white pigment to be contained in the resin-coated layer of a support base, and another proposal for a light sensitive material having a hydrophilic colloidal layer containing a white pigment. It was, however, found that, when an amount replenished is small or with the variations of the processing conditions such as the fatigue of a developer, there arises the problems that a gradation is varied in a toe portion, and that the tone is varied in a high-light portion.
On the other hand, in color plate-making printing processes, an over-lay process, in which a color image is formed by making use of a photopolymer or a diazo compound, and a surprint process are known as a process for obtaining a color proof from a plurality of black-and-white halftone dot images prepared by a color separation and a halftone dot image conversion.
The over-lay process is advantageous, because the operations are very simple, the preparation cost is inexpensive, and the resulting color proof can be used for the proofing purpose only by superposing 4 colored (in the primary colors of subtractive color mixture and in black) film sheets, respectively. However, this process has a defect that the resulting texture becomes different from that of the corresponding printed matter, because a gloss is produced by superposing the film sheets.
The surprinting processes are each to superpose colored images together on a support. As for these processes, the processes in which a colored image is obtained, in a toner development, by utilizing the stickiness of a photopolymerization material, as known from the disclosures in U.S. Pat. Nos. 3,582,327, 3,607,264 and 3,620,726.
As is known from JP Examined Publication No. 47-27441/1972 and JP OPI Publication No. 56-501217/1981, a process for preparing a color proof is carried out in the following manner. An image is transferred onto a support by making use of a light sensitive colored sheet. After the image is formed thereon by exposing to light and then by developing it, another colored sheet is laid thereon and the same processes are then repeated.
JP OPI Publication No. 59-97140/1984 are known to disclose a process in which each of colored images is formed on a support upon transfer of the colored images obtained by exposing color-separated films each corresponding to the colored images to light and then by developing them. It is advantageous to utilize a coloring material similar to a printing ink so as to serve as both of a toner for colored sheet use and the coloring agent for forming these images. Therefore, the tones of the resulting color proof closely resembles that of the resulting printed matter.
In these processes, however, images have to be superposed together and transferred in the color proof preparing step. Therefore, the processes have the defects that it takes a long time to work and that the preparation cost is expensive.
As for the processes capable of solving the above-mentioned defects, there are the processes in which a color proof is prepared by making use of a silver salt color photographic light sensitive material having a white support, as disclosed in, for example, JP OPI Publication Nos. 56-113139/1981, 56-104335/1981, 62-280746/1987, 62-280747/1987, 62-280748/1987, 62-280749/1987, 62-280750/1987 and 62-280849/1987.
In the above-mentioned processes, a color original is converted into the color-separated halftone dot images to prepare a plurality of color-separated black-and-white halftone dot images. The resulting halftone dot images are printed one after another on a sheet of color paper in a method such as a contact printing method and the printed color paper is color developed. A color image is formed of the dye imagewise produced of the couplers, by the color development. The resulting color image is then used as an image for proofing use.
However, the above-mentioned techniques have the defect that the halftone dot reproducibility is liable to be varied particularly in an image region where a narrow halftone dot area is small. Particularly in the case of varying the conditions for the development process, the above-mentioned variations become serious and, therefore, the improvements thereof have been demanded.
When simply making use of the light sensitive material having a hydrophilic colloidal layer containing the white pigment, described in the foregoing JP Examined Publication No. 2-29203/1990, as a light sensitive material for proofing use, it was further found that the small dot reproducibility is deteriorated, in a region where the halftone dot area is small, when the light sensitive material is subject to a running treatment or a fresh sample preservation.